she comes across as way more emotional than the average Vulcan; she seems unusually haughty, disrespectful, and petty.

I really think the writers were trying to make the Vulcans be haughty, disrespectful and petty. The two species did not have the same relationship as they did in TOS; one of mutual respect. During the "Enterprise" time-frame; Vulcans thought very little of humans and did not respect them as equals and did not think they needed to be out exploring the galaxy (since they didn't understand the human emotions; it made the Vulcans think of them as a lower species). I think Blalock's performance was meant to convey that and personally I think she does a pretty good job. It's nice to see the change in her characters attitude towards humans as the series progresses and I think her being on an "Earth ship" and the relationship established with the humans is the first time the Vulcans begin to consider the human race more as equals and we get to see that unfold in this series.